Slotted waveguide antennas are well known and utilized in the art for emitting microwave electromagnetic field of desired polarization, e.g., vertical, horizontal or circular.
For example, U.S. Pat. No. 3,740,751 to Nemit describes a slotted-waveguide array having a dual-slot configuration. The pattern of the array sub-group has a null in the direction at which a grating lobe would occur in an antenna having single slot-element per radiator.
U.S. Pat. No. 3,523,297 to Fee describes a dual frequency antenna array that is composed of slotted hollow fin trough waveguide with obstacles located on the sides of the hollow center fin. The trough guide with obstacles located on the sides of the hollow center fin is the low frequency section of the antenna. The slotted hollow center fin, on the other hand, constitutes the high frequency section of the antenna.
U.S. Pat. No. 5,541,612 to Josefsson describes a waveguide antenna that includes a pair of waveguides having two super-imposed single-mode hollow waveguides which are mutually separated by a partition wall. Electromagnetic waves having two mutually perpendicular polarizations are emitted through separate antenna ports, which are comprised of two separate arrays of slots in the upper wall of the upper waveguide. Selected polarization of one transmitted electromagnetic field can be obtained by varying the amplitude and phase of the signals to respective antenna ports.
U.S. Pat. No. 5,638,079 to Kastner et al describes a slotted waveguide array antenna comprising a plurality of waveguide elements extending in a parallel side-by-side relation. A radiating side is formed with a plurality of slots. The slots are slanted to the longitudinal axis of the antenna in alternating directions and are spaced apart such as to offset phase reversal between each pair of adjacent slots. The slotted waveguide array antenna also includes an asymmetric ridge formed on a non-radiating side opposite to the radiating side.
U.S. Pat. No. 5,831,583 to Lagerstedt et al describes a waveguide antenna that includes a number of longitudinal waveguides with lateral and longitudinal slots arranged to emit electromagnetic fields with separate directions of polarization. The waveguide antenna includes a first waveguide having a first rectangular cross-section with lateral slots at substantially right angles with respect to the longitudinal axis of the first waveguide. The lateral slots are arranged in a first short side of the first waveguide. The waveguide antenna also includes a second waveguide having a second rectangular cross-section with longitudinal slots arranged in a second short side at substantially right angles with respect to the lateral slots, and a separating wall. The first and second waveguides are joined at respective first and second broad sides with the first and second short sides facing the same direction.
U.S. Pat. No. 6,731,241 to Park et al describes a dual-polarization common aperture antenna that includes firs and second arrays of radiating slots disposed in a faceplate. The second array is orthogonal and therefore cross-polarized relative to the first array. The first array and the second array share a common aperture.